<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>CSS3过渡</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            background: red;
            transition: 2s;
        }
        div:hover {
            width: 200px;
            height: 200px;
            -webkit-transform: rotate(180deg); /* Chrome, Safari, Opera */
            transform: rotate(180deg);

        }
    </style>
</head>
<body>
<div>鼠标移动到 div 元素上，查看过渡效果。</div>
</body>
<html>
